Elapid and Viperid Snake Venoms in the U.S.: How do they differ?

For anyone who thoroughly enjoys thinking about complicated biochemistry, investigating the chemistry of snake venoms should be a priority! A discussion of differences in venom types is very complex, necessitating a basic overview of venom biology. The following post describes information focused on mainly snakes in the U.S. for reasons of simplicity and overall understanding.  In the U.S., important venomous snakes are grouped in the family Viperidae, the vipers (i.e. viperids), specifically pitvipers, and Elapidae (i.e. elapids), specifically coralsnakes, which are cobra-related.  In Colorado, only the pitvipers occur, elapids being found in Arizona, Texas, and seven states in the southeastern U.S.  Pitvipers in the U.S. are comprised of rattlesnakes, cottonmouths, and copperheads, while the elapid group consists of 3 species of coralsnakes (SSAR).  In comparing these two groups, venom differences occur based on different factors, such as types of prey, which contributes to complex combinations of venom chemical components.

Venom is basically a highly evolved derivative of saliva that certain snakes use primarily to subdue and secure prey.  Secondarily, the application of venom can be a defensive tactic delivering negative feedback to a predator (or human).  Venom in general is a magnificently super-complex poison sometimes exceeding 100 chemical components, consisting of proteins, peptides, and enzymes.  Despite the small amounts that are injected into prey, there are severe, rapid changes that can occur to many of the body’s organ systems through cellular disruption.  Components are frequently categorized according to the organ systems or cells that they affect, namely, cardiotoxins (affecting the heart), hemotoxins (destroying blood cells and vessels), myotoxins (disrupting muscle nerve impulses), and neurotoxins (primarily affecting muscles, especially those associated with breathing).  These components can occur together in astonishingly variable amounts between families of venomous snakes, as well as species and even individuals within the range that they occur.  Venom components are designed to work together in a complimentary way that amplifies the characteristics of each component.  

​Let’s now look into pitviper and elapid venom group types and discover why they differ and how. With pitvipers, the diversity of prey types consumed is extensive, primarily consisting of mammals, but also including birds, lizards, anurans, and invertebrates. In order to be able to subdue and secure any suitable prey type by envenomation, there must be sufficiently complex and inclusive venom components available to cover all prey types. Most pitvipers have all four of the aforementioned basic component types in varying ratios, although a few pitvipers have neurotoxins as a dominant venom component, but still maintain the other components. After subduing prey, these components essentially initiate the process of prey breakdown, enhancing additional gastric digestion. Additionally, pitvipers possess amazing teeth, specifically the fangs, that inject appropriate amounts of venom into prey no matter the size. The fangs function as hypodermic syringes and are folded back into the upper jaw when not in use.  In the elapid group, the prey choices of coralsnakes are somewhat more specific, smaller snakes and lizards being dominant on the menu. Coralsnakes have fangs as well, but because of a different skull structure, their fangs are short and fixed in place, not folding back as in pitvipers.  Here, the action of injecting venom frequently requires a sustained chewing action to administer useful amounts of venom. Coralsnake venom contains very little cardiotoxin or myotoxin, instead, there is abundant neurotoxin, which functions to paralyze muscles, including muscles used in breathing.  Apart from venom action on prey species, another significant difference between pitviper and coralsnake venom is the antivenom used to treat envenomations to humans and their pets.  The same pitviper antivenom can be used with virtually all pitvipers in the U.S. However, a notable difference occurs in coralsnakes, where only an antivenom specific to coralsnakes can be used for envenomations by all of the coralsnakes in the U.S.